When I'm walking in my neighborhood, inevitably someone I know drives by in a car. They usually honk and wave, and I wave back. Sometimes I can't see who the person behind the wheel is; I usually acknowledge them with a wave anyway. That way I can't be accused of being stuck up if it really is someone I know.
Oddly, when I'm driving I usually don't see anyone I know, so I don't get to be on the giving end of the wave. The other day I decided it shouldn't matter whether or not I knew a person. The friendly thing to do would be to honk anyway. Besides, I thought it would be fun to see what people did. Today on the way home from work I honked and waved at all the pedestrians I saw.
I got a variety of reactions. Some people waved back, some people looked confused, and some (including all of the children) just ignored me. I think the guy with the i-pod wire running from his pocket to his ear probably didn't even hear me!